This week Xingliang Zhang of Northwest University in China reports in Science the discovery of a new site full of soft-bodied animals that have never been seen before.

For soft-bodied animals to be preserved, something disastrous must take place. In the case of the world's two most famous Cambrian（寒武纪）sites, the Burgess Shale accumulation in Canada and the Chengjiang site, this disaster was a series of storms that dunked vast quantities of mud upon a community of animals, burying them alive.

The new site that Dr Zhang is reporting, known as Qingjiang, is similar to the others in that the animals seem to have been killed by a sudden mud burial. However, that is where the similarities end.

Qingjiang has produced over 20, 000 specimens（样本）thus far. Of these, 4, 351 have been properly analysed and are thought to represent around 100 groups of creatures. Dr Zhang and his colleagues estimate that 54 of these groups have never been seen before.

There are some familiar animals like cnidarians（刺细胞动物），but these also raise quite a lot of questions. Cnidarians exist widely in modern oceans and have simplistic bodies that suggest they evolved early during the rise of animal life. Given this, it was expected that cnidarians would be common in the sedimentary layers when the Burgess Shale and Chengjiang sites were first unearthed. But precisely the opposite proved true.

Qingjiang surprised Dr Zhang by being loaded with spectacularly well-preserved members of this soft-bodied group. Containing everything from delicate comb jellies to the medusae（水 母）,Qingjiang reveals that these animals were well established at the time and rapidly multiplying in some environments. Precisely what these environmental differences were though, remains the subject of considerable inquiry. Anyway, the discovery of the fossils could make clear the diversity of extinct creatures as well as their connection with animals in modern times, said Zhao Fangchen, a researcher of Chinese Academy of Sciences.

【小题1】What is the most probable reason of those soft-bodied animals' being so well-preserved?

A．Existing widely in some environments.

B．Being buried alive by a sudden mud.

C．Being abandoned during evolution.

D．Being well-established at the time.

【小题2】In what way is Qingjiang site different from others?

A．100 groups of creatures were found in Qingjiang site for the first time.

B．Cnidarians were common in Burgess Shale and Chengjiang sites.

C．Cnidarians existed in large numbers in Qingjiang site.

D．The animals were killed by something disastrous.

【小题3】What can we learn about cnidarians from the passage?

A．They became extinct because of sudden mud burials.

B．The environmental differences of their existence are clear now.

C．Their bodies are so simplistic that they can be easily wiped out.

D．They developed at the beginning of the appearance of animal life.

【小题4】What is the main purpose of this passage?

A．To bring us some knowledge about Qingjiang site.

B．To display the diversity of extinct water creatures.

C．To illustrate the significance of archaeology.

D．To distinguish Qingjiang site from others.